Ashless dispersant

Although connection of polyalkylene or poly(alkylene oxide) groups to the polyamine is most commonly by the succinimide linkage, a different linking group is employed in another important class of ashless dispersants— the Mannich bases. They are prepared on a commercial scale by reaction of an alkylphenol with formaldehyde and a polyamine (173—177). The alkyl and polyamine moieties are similar to those used in the succinimide products. 

Lubricant additives (Ashless dispersant A and B, Zinc dialkyldithiophosphate) TT A (Ward et ah, 2002b)... 

Examples of such surfactants are detergents which include calcium and magnesium sulfonates (RSOO)2M2+, phenates (RC6H40)2M2+, carboxylates (RCOO )2M2+, phosphonates RPO/M2 and carbonate-sulfonate hard-core reverse micelles (RMs). Ashless dispersants are the most widely used types, such as the substituted polyisobutylene amine succinimides (mono-substituted, m-PIBS and bis-substituted, b-PIBS), succinate esters, Mannich bases, and phosphorus types, see Chapter 2.2 for formulas (Inoue and Watanabe, 1983 Papke and Rubin, 1992 Vipper and Watanabe, 1981). 

Mixtures of metallic detergents, such as phenates, sulfonates, phosphonates, and salicylates with ashless dispersants such as succinimides and benzylamine, together with zinc dialkyldithiophosphate (ZDDP), can lead to new effects. The possible interactions between these main additives used in lubricating formulations when dissolved/dispersed in hydrocarbon media are shown in Fig. 2.8 together with an indication of the intensity of those respective interactions. 

B) Medium intermolecular interactions detergent-dispersant. In hydrocarbon formulations, the principal interaction between ashless dispersants (e.g., succinimide) and metallic detergents (e.g., phenate, salicylate and sulfonate) may be ascribed to the acid-base interactions between the anion of metallic detergents and the amino group of the succinimide as shown in Fig. 2.10. 

Some investigators have shown that mixtures of succinimides, sulfonates, phenolates and salicylates produce acid-base complexes which tend to form aggregations (Inoue and Watanabe, 1983 Vipper and Watanabe, 1981). The intermolecular interactions between ashless dispersants (PIBS) and metallic detergents were found to decline in the following order ... 

Detergent-dispersant interactions at surfaces. In 4-ball wear tests, an ashless dispersant was found to have an adverse effect on ZDDP-sulfonate-carbonate hardcore RM additives. A high molecular weight Schiff base had the worst effect, followed by a bis-PIBS m-PIBS had the least adverse effect. Interactions among additives affects valve train wear. One of the effects is that a succinimide together with other additives increases the decomposition temperature of ZDDP (Ramakamur, 1994 Shirahama and Hirata, 1989). 

The typical detergent-dispersant additives used in modem lubricating oils are metallic detergents/sulfonates, phenolates, phosphonates, salicylates, ashless dispersants/succinimides and benzylamines. Water is solubilized by strong ion-dipole interactions. The solubilization of water (Watanabe, 1970) by hydrogen bond formation with succinimides and the amount solubilized is smaller than that solubilized by sulfonates. 

Additive containing no metallic elements, e.g., ashless dispersant succinimides, succinate esters. 

PIBSA Polyisobutenyl succinic anhydride precursor for ashless dispersants. 

Use In lubricating-oil additives for ashless dispersant processing, rolling, and compressor oils caulks, sealants, adhesives as an elastomeric process aid and cling improver in cling films. 

Data have been reported showing HSD VI improvers are reported to contribute less viscosity to the CCS than PMA or OCP, permitting the use of a heavier base stock [82], which had a favourable effect on base oil volatility reflected in improved oil consumption. Several reports demonstrated that dispersant PMA or OCP VI improvers in some cases permit a significant reduction in ashless dispersant level for fully formulated engine oils, also permitting use of a heavier base stock [17, 83]. 

Dispersancy It has been pointed out that dispersant PMAs can replace a significant portion of the ashless dispersant necessary for sludge dispersancy performance... 

Before 2001, the components used for specific lubricant functions had remained relatively consistent since the introduction of ashless dispersant technology in the 1960s. However, recently introduced emissions legislation mandates the use of exhaust after-treatment for both gasoline and diesel light vehicles in many parts of the developed world, and this requirement affects component selection for modern formulations. 

Reduced detergent levels can be supplemented by adding ashless dispersants to deliver the necessary piston cleanliness. But the dispersant s high contribution to viscosity means that compromises have to be made elsewhere in the formulation. Dispersants, for example, have a detrimental effect on fuel economy and may lead to restricted choices of basestock and viscosity modifier to meet viscometric requirements. Furthermore, the high active nitrogen content that makes dispersants effective can also cause problems with elastomer compatibility. 

Modern oil formulations now contain high levels of ashless dispersants to keep the soot particles well dispersed. Antiwear additives, mainly ZDDP, have also been boosted to cope with the higher levels of abrasive soot wear. 

Lubricant formulations meeting API CG-4 standard and above have generally contained greater than 0.1% levels of phosphorus. Eurthermore, as the soot levels in lubricants have increased so have the levels of ashless dispersants, typically exceeding 6%. It is believed that the additional dispersant helps to minimise wear by dispersing soot and contributing to the oil film thickness. Lubricants with lower... 

Ashless additive development has reduced the risk of solid deposit formation and ashless dispersants, anti-oxidants and anti-foam agents are now permitted in most engines. Non-dispersant mineral oils are now used primarily for older aircraft and as a running-in oil for new engines or after overhaul. 

Heavy duty detergent oils usually include ashless dispersants within their formulation to keep combustion contaminants in fine suspension to prevent damage to machinery. Warning limits for the insolubles content of trunk piston engine oils vary with the oil but in some cases levels of 5% can be tolerated. When high levels of insolubles are encountered, the fuel and fuel combustion systems should be examined. 

Two types of surfactants are used in engine oil applications. One is ashless dispersants, and the other is metallic detergents. Typical ashless dispersants, as described in Chapter 15 of Part D (Formulations) of the Handbook of Detergents [8], include succinimides, Mannich condensates, esters, phosphonates, functionalized ethylene-propylene copolymers, and others. Their molecular structures are shown in Figure 13.1. 

Though ashless dispersants made by Mannich condensation reaction, functionalized ethylene-propylene dispersants, and succinate ester dispersants can be used in ATF formulations, succin-imide dispersants are more commonly nsed. The dispersants used in ATFs have similar chanistries as those described in engine oil applications, except in most cases the molecular weights of the polyisobutyl hydrocarbon chain of the dispersants used in ATFs are lower. Furthermore, the dispersant molecules are reacted with boric acid and caped with additional antiwear chemistries. 

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